An effective electrical connection between a receptacle terminal and a mating plug terminal, such as a socket and pin, is achieved when there is substantial contact force by the contact areas of the receptacle terminal applied normally to corresponding contact areas of the plug terminal when the plug terminal has been fully inserted into the receptacle terminal. A typical active socket terminal has cantilever spring arms having stiff spring characteristics, which arms must be urged apart by the pin terminal during insertion. The force required to insert the pin into the socket, termed the insertion force, may be on the order of 11/2 lbs. Where an electrical plug connector has many such pins and is to be mated with a corresponding socket connector the total mating force is the sum of the individual insertion forces; for instance, in a connector having fifty terminals, each with an insertion force of 11/2 lbs., the total mating force would be 75 lbs. With such a high mating force required, unassisted manual connection is difficult.
Card edge connectors are known to electrically connect two opposing rows of spring contact arms of discrete contacts to conductors on side surfaces of an edge portion of a printed circuit card. So many pairs of spring contact arms are located in such a connector each having an insertion force, presenting a significant overall insertion force required to be overcome to insert a card edge, that many designs of ZIF (zero insertion force) or LIF (low insertion force) connectors have been devised. Usually such connectors utilize a distinct operator actuated camming device having an active position to force the paired spring contact arms apart and hold them apart until the card edge has been inserted therebetween at little or no insertion force, after which the camming device is actuated to a neutral position allowing the spring contact arms to apply significant contact force normally against the respective conductors on the side surfaces of the card edge. One such connector is disclosed in U.S. Pat. No. 3,899,234. Such operator actuation is a separate step requiring either significant manual effort or appropriate separate tooling, or both.